Synaptic inhibition is important for all neuronal networks. Nonetheless, relatively little is known about the learning rules by which inhibitory synaptic strengths are controlled, in development and in adult animals. The goal of this project is to determine whether the inhibitory synapses in the lobster stomatogastric ganglion (STG) show activity-dependent modifications in strength, and whether previously proposed theoretical learning rules capture these modifications. A presynaptic neuron in the STG will be voltage clamped and driven to produce trains of depolarization for extended periods of time. The voltage response of the postsynaptic neuron, held in current clamp, before and after extended presynaptic depolarization will determine the existence and properties of any synaptic modification. The dependence of this modification on postsynaptic voltage and calcium concentration will be investigated. These experiments will motivate development of theoretical synaptic modification rules which will be implemented in biologically realistic model neurons results will also motivate modeling of coincident tuning of synaptic and intrinsic conductances.